1. Technical Field
The present invention relates to photoresist compositions for EUV and methods for forming photoresist patterns using the same. More specifically, the method for forming less than 50 nanometers (nm) fine photoresist patterns without collapse thereof are disclosed by using a negative photoresist composition comprising a melamine derivative and polyvinylphenol and using EUV (Extreme Ultraviolet) as an exposing light source.
2. Background of the Related Art
As device design of semiconductors become smaller, it is impossible to form less than 50 nm microfine photoresist patterns using KrF (248 nm) and ArF (193 nm) and general photoresists. Recently, a lithography process has been developed to integrate many circuits in a smaller area by using light sources of short wavelength and chemical amplification type DUV (Deep Ultraviolet) photoresists which react with above short wavelength light.
The short wavelength light sources are EUV (Extreme Ultraviolet) (13 nm), ion-beam, and X-ray. Since EUV makes possible to design circuits of less than 0.1 micrometers (μm), it expects that semiconductor devices having 100 times more capacity and 100 times faster speed than those manufactured by currently used processes can be manufactured by a process using EUV.
In the DUV photoresist, a photoacid generator therein produces acid when illuminated by the light source, and the main chain or branched chain of a matrix polymer reacts with the produced acid in the baking process and is decomposed or crosslinked, so that polarity of the polymer is considerably altered. This polarity alteration results in a solubility difference in a developing solution between an exposed area and an unexposed area.
For example, in the case of a positive photoresist, acid is generated in the exposed area, and the generated acid reacts with the matrix polymer in the baking process after exposure so that the main chain or branched chain of the polymer is decomposed and dissolved in a subsequent developing process. In the case of a negative photoresist, acid is produced in the exposed area, and the main chain or branched chain of the polymer causes a cross-linking reaction by the produced acid and becomes insoluble. As a result, the polymer is not dissolved in the subsequent developing step, thereby forming a negative image of a mask on a substrate.
As described above, since resolution in the lithography process depends on wavelength of a light source, more microfine patterns may be formed using the light source of smaller wavelength. In order to practically realize the technology forming microfine patterns of less than 50 nm, photoresist materials such as the photoresist having high sensitivity to ion-beam radiation or the EUV as well as cost-effective exposing and irradiating equipment suitable for EUV are required.
However, in the current lithography process to form patterns of less than 50 nm by using a conventional photoresist and EUV, the patterns are collapsed after development. As a result, a lithography process preventing pattern collapse after development is required.